did a quick google before submitting this reply, I guess you won't really find pure tin too much outside of science labs... its all alloys now What Are Tin Cans Made Of? | eHow

About Tin
While tin is technically considered a "common" metal instead of a precious metal like gold, tin is still rare. It may be the least available of all common metals. This means that making anything out of pure tin---especially common objects---would be difficult and very expensive. Indeed, only a certain number of tin mines exist throughout the world, and scientists are already pinpointing dates when they will be mined dry. So most tin cans are combined with other types of metals to form alloys.

Tin Plate

You will usually only see pure tin as tinfoil (not aluminum foil), which is used for scientific projects or to wrap other objects, such as candy bars. Because tin can be flattened to such a thin sheet, a small amount goes a long way. One pound of tin can produce as much as 130 square feet of tinfoil. Tin does not interact with oxygen and lose its molecular structure (meaning that it cannot rust); it is highly resistant to corrosion by acidic substances and does not tarnish.

Most tin is used to make tin-plate. This tin-plate is mostly steel (or iron, depending on the use and expense involved) and only 1 to 2 percent tin, which forms a coating over the metal to protect it from the elements. This allows tin to be used for a vast number of commercial objects, such as tin cans. Originally and even to this day, the main purpose of tin cans is to preserve food. Ordinary metals would react to the acids that foods naturally produce and begin to corrode, releasing molecules that both destroyed the can and contaminated food. In the past, this was a significant problem with lead, which would leach out dangerous toxins into the food packaged in lead cans. Tin, on the other hand, since it's resistant to acidic combinations, is able to safely hold food for a long period of time without corroding.

Modern Cans
Of course, tin is only the traditional way to make cans. Many cans today are made of aluminum or different types of treat metal, as long as that metal can be formed into the can shape and is resistant to corrosion and rust. Both older tin cans and newer versions are recyclable, which allows manufacturers to strip away the tin and other valuable parts of the can and use the steel or iron for scrap metal.

The scrap yard here just counts any very thin steel as tin. It don't matter if it actually is or not, sheet metal that is not aluminum and not thick enough to get classified as #1 or #2 gets counted as tin. Appliances, car bodies, steel tools, all get counted as tin. Car frames and things like that get counted as #2 long iron and pay more, and the really thick stuff like car rotors, I beams, etc. get labeled #1 long iron and pay even more.

For that reason I usually just keep a magnet with me. If the magnet sticks, it's steel, if it doesn't, it's aluminum. Copper and things are easy to tell apart visually, and I usually do the heavy steel loads (#2 or #1) as separate trips to avoid confusion, unless it's just a little bit, in which case I just unload the bulk of the load first, weigh empty, and then hand carry the items over to the scale where they weigh pop cans and stuff.

One of the yards I deal with has a separate price for "clean tin". I sell all computer shells, shelving units, and any other sheet or stamped steel that is clean of plastic or anything else as this. Everything else is considered "shredder" price. Clean tin pays $.02 more than shredder. Another yard classifies almost everything irony as tin. Different yards, different buyers, different ways of doing things.